Substrate conveying modules of this kind are known in particular in the semiconductor industry. The substrates used therein are on the one hand disk-shaped wafers that are usually made of silicon or gallium arsenide. Substrates can, however, also be masks, i.e. glass plates on which patterns have been or are applied, and which serve as originals for exposing wafers.
In the production of semiconductor wafers, between certain production steps the substrates are transported, in cassettes of various kinds, to different workstations and must there be inserted into the respective workstation. Transport can be accomplished manually or automatically.
The workstations serve various purposes for treatment of the substrates, such as inspection, measurement, or processing of the substrates. During inspection of the particles on the substrates, or defects in the patterns on or in the surface of the substrates. Inspection can be accomplished by the user, or automatically by way of an electronic camera. In these or in separate workstations, measurements can also be performed on the substrates. For example, the unwanted particles or pattern defects can be automatically detected and classified (defect analysis). The widths, spacings, or thicknesses of the patterns can furthermore be measured (CD analysis, layer thickness analysis). Because the objects being investigated are small, microscopes are usually used for these inspection and measurement applications in such workstations. In addition, macro-scale inspection of the substrates is possible; in this, the entire substrate is visually observed under light at a specific angle of incidence, so that scratches, resist defects, or dirt particles can be detected very quickly. The inspection and measurement procedures are often fully automated, both in terms of handling of the substrates and as regards the locations on the substrate to be inspected or measured.
In other workstations, the substrates are processed, e.g. patterns are generated by depositing specific substances or by way of etching operations, or resists are applied for exposure.
Other usual criteria for such workstations and substrate conveying modules are high reliability and ease of use. They should require only a small floor space (“footprint”) in the valuable clean-room space in the manufacturing facility.
In particular, however, they should be designed so they are easy and simple to maintain. At the same time, stringent requirements are imposed on the handling of the substrates, for example in terms of handling reliability, speed, and cleanliness. In addition, it should also be possible for substrates of different diameters to be used and to be introduced into the handling system. In this context, “handling” of the substrates means transferring the substrates from the substrate conveying module into the workstation, and changes in location within the workstation and lastly back out into the substrate conveying module, optionally with appropriate sorting.
In order to meet these many and stringent requirements, existing substrate conveying modules and workstations are immovably connected to one another from the outset, and are supplied to the semiconductor manufacturer as a unit. In this context, the semiconductor manufacturer must indicate from the outset the point on the workstation—i.e. on the left or right side or at the rear of the workstation—at which the substrate conveying module is to be installed and connected. The orientation of the substrate conveying module with respect to the workstation must also be predefined. This determines the point on the substrate conveying module at which the latter can be loaded with the substrate cassettes. The future user must therefore indicate in advance the particular side of the substrate conveying module on which the loading of substrates from outside is to be accomplished.
As an alternative to complete prefabrication, it is also possible for installation of the substrate conveying module and individual modules of the workstation to be delayed until they are within the manufacturing facility, and performed by the semiconductor manufacturer. In this case as well, however, a decision must be made from the outset as to the arrangement in which the substrate conveying module is to be combined with the workstation, i.e. at what point and with what orientation the substrate conveying module is to be coupled to the workstation.
U.S. Pat. No. 5,399,531 discloses a manufacturing system for semiconductor wafers in which a plurality of process stations is connected to a permanently defined, branched transport system for the wafers that has load zones and unload zones.
U.S. Pat. No. 5,842,824 describes a substrate transport apparatus for an exposure device in which a substrate supported in a vertical orientation is transported along a path and, after the substrate has been changed into a horizontal position, the substrate is brought via a pre-alignment mechanism onto a substrate stage. No provision is made for a flexibly modifiable arrangement of the substrate transport apparatus with respect to the pre-alignment mechanism with substrate stage.